You Must Remember This
by foobar137
Summary: A mad scientist is threatening Danville; in order to stop him, Perry has revealed that he's a secret agent, and now he's begging Isabella to kiss Phineas. This wasn't how she envisioned their first kiss... Stand-alone Phinbella one-shot. Trope bingo: "A Kiss To Save The Day".


**Trope bingo square: 'a kiss to save the day'.**

**Partly inspired by karly05's "The Other Kiss". Not related to any other timeline of mine.**

* * *

The platypus was begging her.

_This really isn't the time or place,_ Isabella thought. _I've loved Phineas for years, but hiding out from evil robots is hardly the right situation for me to go give him a kiss._

Perry dropped to his knees in front of her, pleading, holding his hat in his hands.

_He seems to think it's important. Maybe he thinks that it'll make Phineas less upset with him?_

It wasn't as if Phineas could be _more_ upset. A new evil scientist, Doctor Destructo, had attacked the Tri-State Area, and Perry had had to reveal that he was really a secret agent to save her and the brothers from his Destructobots. It had all been explained by the man who called himself Perry's nemesis - they'd been fighting for years, but had teamed up to fend off this new threat.

Phineas had felt horribly betrayed; his pet, the platypus who didn't do much, had really been spending all those missing afternoons out saving the world, and hadn't _once_ let Phineas come along. And now, when they needed Phineas and Ferb and Perry to work together with Perry's nemesis to defeat Doctor Destructo, Phineas wanted nothing to do with the platypus. Not even Ferb's legendary persuasiveness had been able to change his mind.

She looked at Phineas, staring out the window of the small abandoned house they were hiding in, and back at the platypus kneeling in front of her.

_Either this works, and Perry and Phineas can work together again, or it doesn't, and at least Phineas will know how I feel about him before...the end._

Decision made, she walked across the room to Phineas. He heard her approaching, and turned angrily; seeing it was her, he calmed a bit. "What's up, Isabella?" he asked.

She grabbed his arms, and, pulling him toward her, planted a kiss on his lips. She'd wanted to do this for years, and now Perry's plea gave her the cover to finally do it. His surprise quickly dissipated, and he started moving to put his arms around her...and then suddenly stopped.

Memories washed over her. Kissing him like this, when they were two years younger. Memories that were erased, so they would no longer remember...

_Perry, as a secret agent, and the evil scientist that was his nemesis, and a trip to another dimension. Phineas being mad at Perry, but reconciling with him. Phineas and Perry fighting side-by-side._

Phineas broke off the kiss, his eyes wide. He gave her a quick hug, and said, "Thank you, Isabella. We need to talk about...us...later, but right now...I need to go apologize to Perry."

* * *

They'd been herded back down to the lab by Perry's boss. The deal was the same as the last time - a memory wipe of the day's events, or Perry had to go to a new home. It was just the three of them this time, but they'd all agreed. Ferb seemed resigned to the situation. Isabella was a bit wistful that yet another kiss was going to go away, especially since Phineas had seemed to like it quite a bit, but it was what needed to happen.

Phineas returned from the bathroom; he'd needed a quick stop there before the memory wipe, which would apparently put them to sleep. They'd wake up tomorrow morning in their beds, and today would be gone.

He took her hand and smiled regretfully at her they lined up for the memory wipe, then turned to Lieutenant Karl. "Wait a second," he said. "I need to do something first."

He turned to Isabella and said, "I've owed you this for too long. Maybe someday we can do this when we'll both remember it." He put his arms around her, kissing her deeply, and she melted into the kiss as she'd wanted to do for years. The world went away, such that she barely noticed that he slid something into her pocket surreptitiously.

Major Monogram cleared his throat. "Is this necessary? You won't remember it anyway."

Slightly embarrassed, they broke off the kiss, looking into each other's eyes as if trying to make such strong memories that they could never be wiped. He took her hand again, and stood next to her. "Go ahead, Carl," he said.

* * *

Perry carefully put Phineas into his pajamas and laid him in bed, then checked the pockets of his discarded pants. _As I thought. He left himself a note._ Written on a paper towel from the bathroom were two words: **Kiss Isabella.** Regretfully, Perry took the note and hid it under his hat. He'd have to keep it, much as he'd like to leave it to be found; while the new memory-wipe was better, he'd have to stop them from kissing for a couple days to prevent their memories from returning again. He looked through Ferb's pockets as well, just to be sure, and found another note. Ferb had written it in the secret Elven language from Stumbleberry Finkbat, but fortunately Perry had learned it by watching over his shoulder. It said: **Tell Phineas to kiss Isabella.** He shook his head sadly and put it with Phineas's note. _Maybe I can give them these notes in a week or two._

_Hopefully Pinky remembers to check Isabella's pockets, too. If she's carrying a note, we could have a problem._

* * *

Isabella woke up the next morning with a nagging suspicion that something wasn't right. The radio DJ was claiming it was Thursday, but she'd swear that yesterday had only been Tuesday.

She showered and got dressed, and then grabbed her laundry basket for the trip downstairs. She let Pinky out into the backyard, then went into the laundry room to start her laundry. Quickly checking her pockets, she found something unexpected. Puzzled, she pulled it out; it was a folded-up paper towel with **Open Me** written on it in Phineas's handwriting. She unfolded it, and read:

**Isabella, don't let anybody else see this note. Destroy it after you've read it. This is important. It's especially important that you don't let Perry or Pinky see it.**

**Find a way to get me alone, and kiss me. Don't tell anyone what you're doing, even me. I won't understand yet. It'll all make sense afterwards. Trust me on this. Please.**

**Love, Phineas.**

_Love, Phineas?,_ she thought. _He's telling me to kiss him?_ She looked at the note more closely. It was clearly Phineas's handwriting. She pinched herself to confirm she wasn't dreaming.

_What's going on here? What's the deal with Perry and Pinky?_

* * *

Phineas noticed that Isabella seemed distracted as they planned out a way to get the Fireside Girls their Recycling patch by building a large paper-powered machine that they could drive around town to gather up recyclable goods.

As people started to go about their tasks, she asked him to come around to the side of the house. Puzzled, he went with her. She looked around, as if confirming that the coast was clear, and suddenly wrapped her arms around him. Her lips met his, and she was kissing him, as he'd dreamt of and feared. _Wait, are we ready for this?_

And then memories came back: two lost days, and three lost kisses. Isabella broke the kiss; her face, mere inches away, looked as shocked as he felt. He smiled at her. "You got my note! They must have found the one I left for myself - I thought they would, I planned it as a decoy."

Disappointment appeared in Isabella's face. "Oh. That's all this was, getting our memories back," she said, turning away from him.

"Wait," he said. "Yes, I wanted to get our memories back - but not the memories of Perry. Not just those ones, anyway."

She turned back toward him and gave him a puzzled look.

"I really wanted these memories," he said, and he pulled her in for another kiss: one that, finally, they would never forget.

* * *

**The title comes from the song As Time Goes By (most famously seen in Casablanca); the next words are 'A kiss is just a kiss', which seems just as apropos.**


End file.
